Slow Twitch Muscle Fibres

Adapted for slow rythmical contractions but still contract fast enough for all sporting activities

Smaller in size to fast twitch

Produce less overall force than fast twitch

More energy efficient than fast twitch - producing more force for the same energy input, this making them well edapted for prolonged/endurance exercise (gets ATP from primarily aerobic energy pathways)

High aerobic capacity = greater no. of blood capillaries for the delivery of O2/fibre than fast twitch

Fast Twitch Muscle Fibres

Best suited to anaerobic exercise = produce their energy primarily from anaerobic pathways

Well adapted to short intense bursts of effort

They ahve a larger diameter as they have more myosin filaments in them. This myosin is thicker than that found in slow twitch fibres

Able to produce more force due to the thicker myosin arrangement in the myofibrils. This greater force of contraction is helped by having a more complex arrangement of Sarc Ret = Ca+ can be released & returned to storage quicker than slow twitch

Have a different myosin-ATPase that releases energy quicker than the type found in slow-twitch fibres